THE DEVELOPMENT OF LATENT FINGERPRINTS ON PAPER.

The article presents information about the development of latent fingerprints on paper. The development of latent fingerprints on paper is very difficult. Since the possibility of obtaining one or more fingerprints on paper objects in actual case work is determined by many factors, it is never easy to determine accurately the length of time after handling that identifiable fingerprints may be secured. Occasionally, on questioned documents or other paper materials, fingerprints are left which can be clearly seen and require no treatment for the purpose of any analytical study. The perspiratory secretion, which arises from the sweat glands of the skin and continuously deposited through the pores onto the friction ridges of the hands, contains 98% or more water with minute quantities or traces of sodium and potassium chlorides, lactic acid, albumin, glucose, urea, fatty acids, phosphates, carbonates, sulphates, creatine and creatinine. This secretion, along with a small quantity of sebum, which is picked up by contact of the hands with hair-producing skin, forms the somewhat transient, latent image from which a clearly visible pattern is to be derived.